Method of manufacturing a color filter

ABSTRACT

A method of forming a color filter is provided. The method includes providing a mixture of a color filter material and a compressed fluid; providing at least a partially controlled environment for retaining a substrate, the at least partially controlled environment being in fluid communication with the mixture of the color filter material and the compressed fluid; providing a shadow mask in close proximity to the substrate retained in the at least partially controlled environment; and chargably releasing the mixture of the color filter material and the compressed fluid into the at least partially controlled environment, wherein the color filter material becomes free of the compressed fluid prior to contacting the substrate at locations defined by the shadow mask thereby forming a patterned deposition on the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/313,587, filed Dec. 6, 2002 and assigned to theEastman Kodak Company.

[0002] This application is related to Ser. No. 10/313,549 filed Dec. 6,2002; and assigned to the Eastman Kodak Company.

FIELD OF THE INVENTION

[0003] This invention relates generally to deposition from compressedfluids and, more particularly, to patterned deposition from compressedfluids onto suitable substrates with the use of masks.

BACKGROUND OF THE INVENTION

[0004] Color filters and the methods used to manufacture color filtersare known. Color filter producing methods include techniques thatdeposit color filter material onto a prepatterned substrate. Thesetechniques include, for example, vapor deposition, spin-coating, andthermal deposition (see, for example, U.S. Pat. No. 5,874,188, issued toRoberts et al., on Feb. 23, 1999).

[0005] Other methods of manufacturing color filters involve evaporatingthe color filter material, using heat or ion bombardment, and thendepositing the evaporated color filter material onto a substrate using acondensation process or a chemical reaction. In these manufacturingprocesses, the color filter material must to be thermally stable or havea thermally stable precursor that generates the color filter material onthe substrate (when a chemical reaction process is used). As is known inthe art, these processes are not adapted to generate patterned layers ofthermally unstable color filter materials.

[0006] Typically, color filters are formed as a continuous film or andarray of pixels. They can include a single color material or multiplecolor materials (for example, combinations of red, green, and blue; orcyan, magenta, yellow, and black). When multiple color materials areused, the color filter is typically formed using pixels in a twodimensional array. Conventional color filter materials are typicallycomposed of organic and organometallic pigments, semiconductors,ceramics, and combinations thereof.

[0007] Inkjet printing systems are commonly used to createhigh-resolution patterns on a substrate. In a typical inkjet printingsystem, ink droplets are ejected from a nozzle towards a recordingelement or medium to produce an image on the medium.

[0008] When used to create a color filter, the ink composition, orrecording liquid, ejected by the inkjet printing system comprises acolor filter material, such as a dye or pigment or polymer, and a largeamount of solvent, or carrier liquid. Typically, the solvent is made upof water, an organic material such as a monohydric alcohol, a polyhydricalcohol or mixtures thereof. The ink composition usually includesadditives designed to preserve pixel integrity after the droplet isdeposited on the recording element, or substrate, due to the highconcentrations of solvents in conventional color filter inkformulations. Additive materials may include surfactants, humectants,biocides, rheology modifiers, sequestrants, pH adjusters, andpenetrants, etc.

[0009] U.S. Pat. No. 6,245,393 B1, issued to Thompson et al., on Jun.12, 2001, discloses a method of making a multicolor display device. Thedevice includes a transparent substrate and a fluorescent dye depositedin a dye layer on the substrate using inkjet printing. This method isdisadvantaged because the ink compositions, which include the colorfilter material, have high solvent concentrations which enables theejection of the ink composition using conventional inkjet printers. Assuch, processing steps devoted to the removal of the solvent(s) arerequired. Additionally, the color filter materials used will not alwaysdissolve or solubilize in commonly available solvents. This cannecessitate the use of exotic solvents that are environmentally harmfuland/or expensive.

[0010] Technologies that use supercritical fluid solvents to create thinfilms are also known. For example, R. D. Smith in U.S. Pat. No.4,734,227, discloses a method of depositing solid films or creating finepowders through the dissolution of a solid material into a supercriticalfluid solution and then rapidly expanding the solution to createparticles of the marking material in the form of fine powders or longthin fibers, which may be used to make films. There is a problem withthis method in that the free-jet expansion of the supercritical fluidsolution results in a non-collimated/defocused spray that cannot be usedto create high resolution patterns on a receiver. Furthermore, Smithdoes not teach the use of a mask to create high resolution patterns on areceiver.

[0011] Other technologies that deposit a material onto a receiver usinggaseous propellants are known. For example, Peeters et al., in U.S. Pat.No. 6,116,718, discloses a print head for use in a marking apparatus inwhich a propellant gas is passed through a channel, the marking materialis introduced controllably into the propellant stream to form aballistic aerosol for propelling non-colloidal, solid or semi-solidparticulate or a liquid, toward a receiver with sufficient kineticenergy to fuse the marking material to the receiver. There is a problemwith this technology in that the marking material and propellant streamare two different entities and the propellant is used to impart kineticenergy to the marking material. When the marking material is added intothe propellant stream in the channel, a non-colloidal ballistic aerosolis formed prior to exiting the print head. This non-colloidal ballisticaerosol, which is a combination of the marking material and thepropellant, is not thermodynamically stable/metastable. As such, themarking material is prone to settling in the propellant stream which, inturn, can cause marking material agglomeration, leading to dischargedevice obstruction and poor control over marking material deposition.

[0012] Huck et al., in WO 02/45868 A2, disclose a method of creating apattern on a surface of a wafer using compressed carbon dioxide. Themethod includes dissolving or suspending a material in a solvent phasecontaining compressed carbon dioxide, and depositing the solution orsuspension onto the surface of the wafer, the evaporation of the solventphase leaving a patterned deposit of the material. The wafer isprepatterned using lithography to provide the wafer with hydrophilic andhydrophobic areas. After deposition of the solution (or suspension) ontothe wafer surface followed by the evaporation of the solvent phase, thematerial (a polymer) sticks to one of the hydrophobic and hydrophilicareas. The solution (or suspension) is deposited on the wafer surfaceeither in the form of liquid drops or a feathered spray.

[0013] This method is disadvantaged because deposition using a featheredspray requires that the wafer surface be prepatterned prior todeposition. Hence, direct patterning of the wafer surface is notpossible because of the diverging profile (feathered) of the spray.Additionally, a wafer surface that has not been prepatterned cannot bepatterned using this method. This method also requires time for dryingso that the solvent phase of the liquid drops (or feathered spray) canevaporate. During the time associated with solvent phase evaporation,the solvent and the material can diffuse (for example, into the surfaceor along the surface) degrading the desired pattern

[0014] Further, those skilled in the art will appreciate that it iscommon to use a mask technique for patterned deposition. Typically, themask employed for patterning on a planar substrate surface is aphotoresist material. However, when the surface is nonplanar,difficulties can be encountered in depositing and cleaning off thephotoresist material, necessitating the use of shadow masks or stencils.For example, U.S. Pat. No. 4,218,532 titled “Photolithographic TechniqueFor Depositing Thin Films,” issued Aug. 19, 1980 to Dunklebergerdiscloses a method for patterned deposition of thin films of metals,such as lead alloys, by vacuum evaporation onto a substrate throughopenings in a mask fabricated with a predetermined pattern. Ashortcoming of this development is that it cannot be used for thepatterned deposition of thermally unstable color filter materials sincethese are not suitable for vacuum evaporation.

[0015] In U.S. Pat. No. 4,013,502 titled “Stencil Process For HighResolution Pattern Replication,” issued Mar. 22, 1977 to Staples, aprocess for obtaining high-resolution pattern replication using stencilsis disclosed. The stencil in Staples is a mask effecting molecular beamdeposition of thin films onto a substrate through openings in thestencil. In this deposition process, the molecular beam source is anelectron-beam evaporator. Much like the Dunkleberger development, ashortcoming of Staples' technology is that it cannot be used forpatterned deposition of thermally unstable materials that are notsuitable for evaporation using an electron beam evaporator.

[0016] Furthermore, it is well known that patterned deposition ofthermally unstable materials on substrates may be achieved by liquidphase processes such as electroplating, electrophoresis, sedimentation,or spin coating but these processes are system specific. For example, inthe case of electroplating, it is necessary that an electrochemicallyactive solution of the functional material precursor is available. Inthe case of sedimentation and spin coating, a stable colloidaldispersion is necessary. In the case of electrophoresis, it is alsonecessary that the stable colloidal dispersion be charged.Microfabrication of multi-layer structures usually requires multiplestages, necessitating the complete removal of residual liquids/solventsat the end of every stage, which can be very energy, time, and costintensive. Further, many of these liquid-based processes require the useof non-aqueous liquids/solvents, which are hazardous to health and thedisposal of which can be prohibitively expensive. For example, in U.S.Pat. No. 5,545,307 titled “Process For Patterned Electroplating,” issuedAug. 13, 1996 to Doss et al., a process is disclosed for patternedelectroplating of metals onto a substrate 14 through a mask. The Doss etal. process, however, has at least two major shortcomings. First, it isonly applicable to materials that have electrochemically activeprecursors. Second, it uses an aqueous electroplating bath for theprocess that requires the coated substrate be cleaned and then dried atthe end of the coating process.

[0017] Moreover, it is well known that to eliminate the need forpotentially harmful solvents that need drying, it is possible to useenvironmental and health-benign supercritical fluids such as carbondioxide as solvents. For example, in U.S. Pat. No. 4,737,384 titled“Deposition Of Thin Films Using Supercritical Fluids,” issued Apr. 12,1988 to Murthy et al., a process is disclosed for depositing thin filmsof materials that are soluble in supercritical fluids onto a substrate.Murthy et al. include the steps of exposing a substrate at supercriticaltemperatures and pressures to a solution comprising a metal or polymerdissolved in water or a non-polar organic solvent. The metal or polymeris substantially insoluble in the solvent under sub-critical conditionsand is substantially soluble in the solvent under supercriticalconditions. Reducing the pressure alone, or temperature and pressuretogether, to sub-critical values cause the deposition of a thin coatingof the metal or polymer onto the substrate. Nonetheless, a shortcomingof the process of Murthy et al. is its limited applicability tomaterials that can be dissolved in compressed fluids, severely limitingthe choice of materials that can be deposited on a substrate using thistechnology. Another shortcoming of the process of Murthy et al. is thatit does not teach a process for the patterned deposition of functionalmaterials.

[0018] In U.S. Pat. No. 4,582,731 titled “Supercritical Fluid MolecularSpray Film Deposition and Powder Formation,” issued Apr. 15, 1986 toSmith, and U.S. Pat. No. 4,734,227 titled “Method Of MakingSupercritical Fluid Molecular Spray Films, Powder And Fibers,” issuedMar. 29, 1988 to Smith, independent processes are disclosed forproducing solid films on a substrate by dissolving a solid material intosupercritical fluid solution at an elevated pressure. In both cases, thesupercritical fluid solution is then rapidly expanded in a region ofrelatively low pressure through a heated nozzle having a relativelyshort orifice. Both of the aforementioned Smith processes have similarshortcomings to those indicated above, i.e., they are only applicable tomaterials that are soluble in compressed fluids and do not teach aprocess for patterned deposition. There is another problem with thismethod in that the free-jet expansion of the supercritical fluidsolution results in a non-collimated/defocused spray that cannot be usedto create high-resolution patterns directly on a receiver. Further,defocusing leads to losses of the marking material

[0019] Therefore, a need persists in the art for a patterned depositionmethod for creating a color filter that permits the patterned depositionof thermally unstable/labile color filter materials and that reduces oreliminates the use of expensive and both environmentally and humanhealth-hazardous solvents. A further need exists for a patterneddeposition method for creating color filter that eliminates the need forpost-deposition drying for solvent-elimination. Moreover, there is anadditional need for a patterned deposition technique that is applicablefor a wide range of color filter materials and that is not limited byspecific properties of the color filter materials.

SUMMARY OF THE INVENTION

[0020] According to one aspect of the invention, a method of forming acolor filter includes providing a mixture of a color filter material anda compressed fluid; providing at least a partially controlledenvironment for retaining a substrate, the at least partially controlledenvironment being in fluid communication with the mixture of the colorfilter material and the compressed fluid; providing a shadow mask inclose proximity to the substrate retained in the at least partiallycontrolled environment; and chargably releasing the mixture of the colorfilter material and the compressed fluid into the at least partiallycontrolled environment, wherein the color filter material becomes freeof the compressed fluid prior to contacting the substrate at locationsdefined by the shadow mask thereby forming a patterned deposition on thesubstrate.

[0021] The color filter material can be a first color filter materialand the shadow mask can be a first shadow mask. When this occurs, themethod can also include providing a mixture of a second color filtermaterial and a compressed fluid; providing a second shadow mask in closeproximity to the substrate retained in the at least partially controlledenvironment; and chargably releasing the mixture of the second colorfilter material and the compressed fluid into the at least partiallycontrolled environment, wherein the second color filter material becomesfree of the compressed fluid prior to contacting the substrate atlocations defined by the second shadow mask.

[0022] Alternatively, the color filter material can be a first colorfilter material. When this occurs, the method can also include providinga mixture of a second color filter material and a compressed fluid;indexing the shadow mask; and chargably releasing the mixture of thesecond color filter material and the compressed fluid into the at leastpartially controlled environment, wherein the second color filtermaterial becomes free of the compressed fluid prior to contacting thesubstrate at locations defined by the indexed shadow mask.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the detailed description of the preferred embodiments of theinvention presented below, reference is made to the accompanyingdrawings, in which:

[0024]FIG. 1 is a schematic view of a preferred embodiment made inaccordance with the present invention;

[0025]FIG. 2 is enlarged schematic view of a controlled environment inone embodiment of the invention;

[0026]FIG. 3 is a schematic view of an alternative embodiment of anenclosure of the invention

[0027]FIG. 4 is a diagram schematically representing the operation ofthe present invention;

[0028]FIG. 5 is a schematic view of an alternative embodiment of acontrolled environment or deposition chamber useful in the invention;and,

[0029]FIG. 6 is a schematic view of an alternative embodiment of anothercontrolled environment or deposition chamber useful in the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Turning now to the drawings, and more particularly to FIG. 1,system 10, broadly defined, for producing patterned deposition fromcompressed fluids includes a delivery system 12, a deposition chamber,or alternatively controlled environment, 30, and a substrate 14 retainedin the deposition chamber, or alternatively, controlled environment 30.Controlled environment 30 is more typically a deposition chamber, asdescribed in detail below. A typical delivery system 12 contemplated bythe invention is one disclosed, for instance, in commonly assigned U.S.Pat. No. 6,471,327 B2, issued to Jagannathan et al., on Oct. 29, 2002,and titled “Apparatus And Method Of Delivering A Focused Beam Of AThermodynamically Stable/Metastable Mixture Of A Function Material In ADense Fluid Onto A Receiver,” hereby incorporated herein by reference.Each of the disclosed delivery systems is capable of delivering aprecipitate color filter material (as described below) and can be usedin the invention.

[0031] Referring to FIG. 1, delivery system 12, capable of deliveringfluids along fluid delivery path 13 in a compressed state, generallyincludes a source 16 of compressed fluid, a formulation reservoir 18 forcontaining a formulation material, a discharge assembly 20, each beingdescribed in detail in the above U.S. patent applications. Deliverysystem 12 serves several important functions in the invention. Itenables the dissolution and/or dispersal of a selected material into acompressed fluid with density greater than 0.1 g/cc³. Further, asolution and/or dispersion of an appropriate color filter material orcombination of color filter materials in the chosen compressed fluid isproduced in delivery system 12. Moreover, delivery system 12 deliversthe color filter materials as a beam or spray into a deposition chamber30 in a controlled manner. In this context, the chosen materials takento a compressed fluid state with a density greater than 0.1 g/cc³ aregases at ambient pressure and temperature. Ambient conditions arepreferably defined as temperature in the range from −100 to +100° C.,and pressure in the range from 1×10⁻⁸-100 atm for this application.

[0032] As depicted in FIG. 1, controlled environment 30, such as adeposition chamber, is arranged proximate to delivery system 12.Controlled environment 30 is positioned at one end of the fluid deliverypath 13 and adjacent the discharge assembly 20 of delivery system 12. Asillustrated in FIG. 2, substrate 14 to be patterned with depositionmaterial and is suitably arranged within deposition chamber 30. In closeproximity to substrate 14, a mask 22 is preferably used to control thelocation of the deposited color filter material on the substrate 14.

[0033] Referring to FIG. 3, in many applications, it is desirable tomaintain an exact concentration of color filter material within thecontrolled enclosure 31. Whilst open loop systems relying on valveopening times can be used, for greater precision and reliability it isdesirable to use a system such as the one illustrated in FIG. 3.According to FIG. 3, enclosure 31 (applies to enclosures of FIGS. 2, 5and 6) is fitted with at least one viewing window or port 33. Viewingwindow 33 can be used alone to provide a visual indication of theconditions inside the enclosure 31. On the other hand, a viewing window33 is also required to facilitate the use of optical emitters 35 andoptical detectors 37 for the purpose of a more accurate assessment ofthe concentration of color filter material inside the enclosure 31. Theoptical emitter 35 emits a beam of light that travels across the insideof the enclosure 31 and is detected by optical detector 37. This opticaldetector 37 sends an electrical signal to the microprocessor 39 inproportion to the amount of light received (which is a function of theamount of color filter material inside the controlled enclosure 31).This information can be used in many ways, most simply as a check of theprocess, but also as an input to a closed loop control of the inputvalve 24. For example, if the concentration in the controlled enclosure31 is low, the valve 24 is opened allowing more color filter material toenter the controlled enclosure 31. This method relies on the cleanlinessof the viewing windows 33 to be effective, and therefore either byroutine maintenance, calibration, or the application of a like charge asthe particles to the viewing windows 33, the viewing windows 33themselves must be kept free of debris. Skilled artisans will appreciatethat there are many variations and other detection methods that could beapplied to a closed loop concentration monitoring and control methoddescribed above. For example, in an optical detection scheme, theoptical emitter 35 and optical detector 37 could be on the same side ofthe controlled enclosure 31 relying on a reflective surface on theopposite side to reflect the beam. The scope is not limited to opticaldetection, any method that provides an indication of the amount of colorfilter material such as electrical properties, physical properties, orchemical properties could be used.

[0034] Referring back to FIG. 1, a compressed fluid carrier contained inthe source 16 of compressed fluid is any material thatdissolves/solubilizes/disperses a color filter material. Source 16 ofcompressed fluids, containing compressed fluid delivers the compressedfluid carrier at predetermined conditions of pressure, temperature, andflow rate as a compressed fluid. Compressed fluids are defined in thecontext of this application as those fluids that have a density ofgreater than 0.1 grams per cubic centimeter in the defined range oftemperature and pressure of the formulation reservoir, and are gases atambient temperature and pressure. Materials in their compressed fluidstate that exist as gases at ambient conditions find application herebecause of their unique ability to solubilize and/or disperse colorfilter materials of interest in the compressed fluid state, andprecipitate the color filter material under ambient conditions.

[0035] Fluids of interest that may be used to transport the color filtermaterial include but are not limited to carbon dioxide, nitrous oxide,ammonia, xenon, ethane, ethylene, propane, propylene, butane, isobutane,chlorotrifluoromethane, monofluoromethane, sulphur hexafluoride, andmixtures thereof. Due to environmental compatibility, low toxicity, lowcost, wide availability, and non-flammability, carbon dioxide isgenerally preferred.

[0036] Referring again to FIG. 1, formulation reservoir 18 is utilizedto dissolve and/or disperse color filter materials in compressed liquidsor compressed fluids with or without cosolvents and/or dispersantsand/or surfactants, at desired formulation conditions of temperature,pressure, volume, and concentration. The formulation may includeadditives to modify surface tension for charging and wetting viscositythrough the use of rheology modifiers and/or thickeners, stabilizers,binders, and dopants.

[0037] In addition, the formulation reservoir 18 can include a sourcethat electrically charges the material particles prior to the materialbeing ejected from the discharge assembly 20. Charging the particles isan important step in many of the preferred embodiments. Alternatively,the color filter materials can also be chosen such that the color filtermaterial stream becomes charged as it is ejected from the dischargeassembly 20 and does not need additional charging. Additionally,additives that can promote charging of the color filter materials canalso be chosen such that the color filter material stream becomescharged as it is ejected from the discharge assembly 20. Such additivesmay include surfactants such as those disclosed in U.S. patentapplication Ser. No. 10/033,458 filed Dec. 27, 2001, titled “ACompressed Fluid Formulation” by Glen C. Irvin, Jr., et al.

[0038] Further, formulation reservoir 18 can be made out of any suitablematerials that can withstand the formulation conditions. An operatingrange from 0.001 atmospheres (1.013×10² Pa) to 1000 atmospheres(1.013×10⁸ Pa) in pressure and from −25° Centigrade to 1000° Centigradeis preferred. Typically, the preferred materials of construction includevarious grades of high pressure stainless steel. However, the materialof choice is determined by temperature and pressure range of operation.

[0039] Formulation reservoir 18 should be precisely controlled withrespect to the operating conditions, i.e., pressure, temperature, andvolume. The solubility/dispersability of color filter materials dependsupon the conditions within the formulation reservoir 18 and even smallchanges in the operating conditions within the formulation reservoir 18can have undesired effects on color filter materialsolubility/dispersability.

[0040] Any suitable surfactant and dispersant material that is capableof solubilizing/dispersing the color filter materials in the compressedliquid for the required application can be used in this method. Suchmaterials include but are not limited to fluorinated polymers such asperfluoropolyether and silane and siloxane compounds.

[0041] Referring to FIGS. 1 and 4, delivery system 12 is shown in fluidcommunication through orifices/nozzles 28 with enclosed, controlledenvironment 30 that contains substrate 14 and mask 22. According to FIG.1, valve 24 may be designed to actuate with a specific frequency or fora fixed time period so as to permit the controlled release offormulation from formulation reservoir 18 into enclosed environment 30via orifices/nozzles 28. According to FIG. 4, the controlled release ofcolor filter material 40 into enclosed environment 30 results in theevaporation of the compressed fluid 41 and the precipitation and/oraggregation of the dissolved and/or dispersed color filter material 40.The precipitated/aggregated color filter material may be allowed togravity-settle or may be settled using an electric, electrostatic,electromagnetic, or magnetic assist. Mask 22 in close proximity tosubstrate 14 results in the patterned deposition of color filtermaterial 40 on the substrate 14.

[0042] Substrate 14 may be any solid including an organic, an inorganic,a metallo-organic, a metallic, an alloy, a ceramic, a synthetic and/ornatural polymeric, a gel, a glass, and a composite material. Substrate14 may be porous or non-porous. Additionally, the substrate 14 can havemore than one layer. Additionally, the substrate 14 may be flexible orrigid.

[0043] As best illustrated in FIGS. 2 and 4, mask 22 may be physical(separate) or integral. The purpose of the mask 22 is to provide apattern for the deposition of functional solute material. Those skilledin the art will appreciate that mask design and manufacture is wellestablished. Physical masks require direct contact between mask 22 andsubstrate 14. Their advantage is that they are relatively inexpensiveand can be re-used for multiple substrates 14. However, if the substrate14 is delicate, the physical contact may damage the substrate 14.Precise alignment is also difficult. Integral masks 22 are structuresformed on the substrate 14 prior to coating/deposition. Alignment andspacing is easier because the mask 22 is a part of the substrate 14.However, because of the potential need to remove the mask 22 afterdeposition, a subsequent etching step may be necessary, potentiallymaking this more expensive and time-consuming.

[0044] Referring to FIG. 4, nozzle 28 directs the flow of the colorfilter material 40 from formulation reservoir 18 via delivery system 12into enclosed environment 30. Nozzle 28 is also used to attenuate thefinal velocity with which the color filter material 40 enters theenclosed environment 30. In our preferred application, it is desirableto rapidly spread the stream of precipitated color filter material 40using a divergent nozzle geometry. Skilled artisans will howeverappreciate that nozzle geometry can vary depending on a particularapplication, as described in U.S. Patent Application Publication No.2002/011842A1, incorporate herein by reference.

[0045] Operation

[0046] Operation of system 10 will now be described. FIG. 4 is a diagramschematically representing the operation of delivery system 10 andshould not be considered as limiting the scope of the invention in anymanner. The description below uses a single nozzle 28 although multiplenozzles and/or multiple nozzle shapes and/or multiple delivery devicesand shapes are within the contemplation of the invention. (See forinstance other nozzle examples disclosed in U.S. Pat. No. 6,471,327 B2,issued to Jagannathan et al., on Oct. 29, 2002).

[0047] Referring to FIG. 4, a formulation 42 of color filter material 40in a compressed liquid 41 is prepared in the formulation reservoir 18 ofthe invention. Color filter material 40, which may be any material ofinterest in solid or liquid phase, can be dispersed (as shown in FIG. 4)and/or dissolved in a compressed fluid 41 making a mixture orformulation 42. Color filter material 40 may have various shapes andsizes depending on the type of the color filter material 40 used in theformulation.

[0048] According to FIG. 4, the compressed fluid (for example, asupercritical fluid, a compressed gas, and/or a compressed liquid) 41forms a continuous phase and color filter material 40 forms a dispersedand/or dissolved single phase. The formulation 42 (i.e., the colorfilter material 40 and the compressed fluid 41) is maintained at asuitable temperature and a suitable pressure for the color filtermaterial 40 and the compressed fluid 41 used in a particularapplication. The shutter 32 is actuated to enable the ejection of acontrolled quantity of the formulation 42.

[0049] With reference to FIGS. 1 and 4, color filter material 40 iscontrollably introduced into the formulation reservoir 18. Thecompressed fluid 41 is also controllably introduced into the formulationreservoir 18. The contents of the formulation reservoir 18 are suitablymixed using a mixing device (not shown) to ensure intimate contactbetween the color filter material 40 and compressed fluid 41. As themixing process proceeds, color filter material 40 is dissolved and/ordispersed within the compressed fluid 41. The process ofdissolution/dispersion, including the amount of color filter material 40and the rate at which the mixing proceeds, depends upon the color filtermaterial 40 itself, the particle size and particle size distribution ofthe color filter material 40 (if the color filter material 40 is asolid), the compressed fluid 41 used, the temperature, and the pressurewithin the formulation reservoir 18. When the mixing process iscomplete, the mixture or formulation 42 of color filter material andcompressed fluid is thermodynamically stable/metastable in that thecolor filter material is dissolved or dispersed within the compressedfluid in such a fashion as to be indefinitely contained in the samestate as long as the temperature and pressure within the formulationreservoir 18 are maintained constant or in the same state for the periodof the efficient operation of the process (metastable). Thisthermodynamically stable state is distinguished from other physicalmixtures in that there is no settling, precipitation, and/oragglomeration of color filter material particles within the formulationreservoir 18 unless the thermodynamic conditions of temperature andpressure within the formulation reservoir 18 are changed. As such, thecolor filter material 40 and compressed fluid 41 mixtures orformulations 42 of the present invention are said to bethermodynamically stable/metastable.

[0050] The color filter material 40 can be a solid or a liquid.Additionally, the color filter material 40 can be an organic molecule, apolymer molecule, a metallo-organic molecule, an inorganic molecule, anorganic nanoparticle, a polymer nanoparticle, a metallo-organicnanoparticle, an inorganic nanoparticle, an organic microparticle, apolymer micro-particle, a metallo-organic microparticle, an inorganicmicroparticle, and/or composites of these materials, etc. After suitablemixing with the compressed fluid 41 within the formulation reservoir 18,the color filter material 40 is uniformly distributed within athermodynamically stable/metastable mixture, that can be a solution or adispersion, with the compressed fluid 41. This thermodynamicallystable/metastable mixture or formulation 42 is controllably releasedfrom the formulation reservoir 18 through the discharge assembly 20.

[0051] Referring again to FIG. 4, during the discharge process, thecolor filter material 40 is precipitated from the compressed fluid 41 asthe temperature and/or pressure conditions change. The precipitatedcolor filter material 44 is ejected into the deposition chamber orcontrolled environment 30 by the discharge assembly 20. The particlesize of the color filter material 40 ejected into the chamber 30 andsubsequently deposited on the substrate 14 is typically in the rangefrom 1 nanometer to 1000 nanometers. The particle size distribution maybe controlled to be more uniform by controlling the formulation(functional solute materials and their concentrations) rate of change oftemperature and/or pressure in the discharge assembly 20, and theambient conditions inside the controlled environment 30.

[0052] Although not specifically shown, delivery system 12 (FIG. 4),contemplated by the invention, is also designed to appropriately changethe temperature and pressure of the formulation 42 to permit acontrolled precipitation and/or aggregation of the color filter material40 (see for instance U.S. Pat. No. 6,471,327 B2, issued to Jagannathanet al., on Oct. 29, 2002). As the pressure is typically stepped down instages, the formulation 42 fluid flow is self-energized. Subsequentchanges to the conditions of formulation 42, for instance, a change inpressure, a change in temperature, etc., result in the precipitationand/or aggregation of the color filter material 40 coupled with anevaporation of the compressed fluid 41. The resulting precipitatedand/or aggregated color filter material 44 deposits on the substrate 14evenly. According to FIG. 4, evaporation of the compressed fluid 41 canoccur in a region located outside of the discharge assembly 20 withindeposition chamber 30. Alternatively, evaporation of the compressedfluid 41 can begin within the discharge assembly 20 and continue in theregion located outside the discharge assembly 20 but within depositionchamber 30. Alternatively, evaporation can occur within the dischargeassembly 20.

[0053] According to FIG. 4, a stream 43 of the color filter material 40and the compressed fluid 41 is formed as the formulation 42 movesthrough the discharge assembly 20. When the size of the stream 43 ofprecipitated and/or aggregated color filter material 44 is substantiallyequal to an exit diameter of the nozzle 28 of the discharge assembly 20,the stream 43 of precipitated and/or aggregated color filter material 44has been collimated by the nozzle 28. When the size of the stream 43 ofprecipitated and/or aggregated color filter material 44 is less than theexit diameter of the nozzle 28 of the discharge assembly 20, the stream43 of precipitated and/or aggregated color filter material 44 has beenfocused by the nozzle 28. It may be desirable for a deposition chamberinput to be a diverging beam to quickly spread the precipitated and/oraggregated color filter material 44 and dissipate its kinetic energy.Such an input is possible without a nozzle 28.

[0054] Referring again to FIGS. 2, 4 & 5, substrate 14 resides withindeposition chamber 30 such that the stream 43 of precipitated and/oraggregated color filter material stream 44 is deposited onto thesubstrate 14. The distance of the substrate 14 from the dischargeassembly 20 is chosen such that the compressed fluid 41 evaporates priorto reaching the substrate 14. Hence, there is no need for subsequentsubstrate 14 drying processes. Further, subsequent to the ejection ofthe formulation 42 from the nozzle 28 and the precipitation of the colorfilter material 44, additional focusing and/or collimation may beachieved using external devices such as electromagnetic fields,mechanical shields, magnetic lenses, electrostatic lenses, etc.Alternatively, the substrate 14 can be electrically or electrostaticallycharged such that the position of the color filter material 40 can becontrolled.

[0055] Referring again to FIG. 4, it is also desirable to control thevelocity with which individual particles 46 of color filter material 40are ejected from the nozzle 28. Since there may be a sizable pressuredrop from within the delivery system 10 to the operating environment,the pressure differential converts the potential energy of the deliverysystem 10 into kinetic energy that propels the color filter materialparticles 46 onto the substrate 14. The velocity of these particles 46can be controlled by suitable nozzle design (see discussion above) andby controlling the rate of change of operating pressure and temperaturewithin the system. Further, subsequent to the ejection of theformulation 42 from nozzle 28 and the precipitation of the color filtermaterial 40, additional velocity regulation of the color filter material40 may be achieved using external devices such as electromagneticfields, mechanical shields, magnetic lenses, electrostatic lenses, etc.The nozzle design will depend upon the particular application addressed.(See, for instance, U.S. Pat. No. 6,471,327 B2, issued to Jagannathan etal., on Oct. 29, 2002).

[0056] Moreover, the temperature of nozzle 28 may also be controlled.Referring to FIG. 4, the temperature of nozzle 28 may be controlled asrequired by specific applications to ensure that the nozzle opening 47maintains the desired fluid flow characteristics. Nozzle temperature canbe controlled through the nozzle heating module (not shown) using awater jacket, electrical heating techniques, etc. (See, for instance,U.S. Pat. No. 6,471,327 B2, issued to Jagannathan et al., on Oct. 29,2002). With appropriate nozzle design, the exiting stream temperaturecan be controlled at a desired value by enveloping the exiting streamwith a co-current annular stream of a warm or cool inert gas.

Embodiment I

[0057] Referring to FIG. 2, controlled environment 30 is designed foruse at extremes of pressure. Incorporated in the controlled environment30 is a pressure modulator 105. The pressure modulator 105, as shown,resembles a piston. This is for illustration only. Skilled artisans willalso appreciate that pressure modulator 105 could also be a pump or avent used in conjunction with an additional pressure source. An exampleof an additional pressure source is the source 109 of compressed fluid.This source 109 is modulated with a flow control device or valve 108 toenable color filter material to enter the deposition chamber 30 via afluid delivery path 13. The pressure inside the deposition chamber 30 iscarefully monitored by a pressure sensor 103 and can be set at anypressure less than that of the delivery system 12 (including levels ofvacuum) to facilitate precipitation/aggregation. In addition, thedeposition chamber 30 is provided with temperature sensor 104 andtemperature modulator 106. Temperature modulator 106 is shown as anelectric heater but could consist of any of the following (not shown):heater, a water jacket, a refrigeration coil, and a combination oftemperature control devices.

[0058] Referring to FIGS. 1, 2, and 4, deposition chamber 30 generallyserves to hold the substrate 14 and the mask 22 and facilitates thedeposition of the precipitated color filter material 44. To enable amore complete and even distribution of the color filter material 40,electric or electrostatic charges can be applied to the substrate 14and/or mask 22. Through the ejection process in the discharge assembly20, the particles are known to become charged. If desired, additionalcharge can be applied to them using a particle charging device 107 (FIG.2). The color filter material 40, now charged can be attracted orrepelled from various surfaces to aid in the deposition process.According to FIG. 2, charging devices 102 a, 102 b are provided for boththe substrate 14 and mask 22, respectively. For illustrative purposesonly, a positive charge (+) is shown on substrate 14 and a negativecharge (−) is shown on mask 22. The polarity may be changed to suit theapplication. A charge equal to that of the color filter material 40 isapplied to the mask 22, whereas a charge opposite of that of the colorfilter material 40 is applied to the substrate 14 to attract the colorfilter material. Obviously there can be no electrical conduction betweenthe two to maintain the charge differential. This may limit the materialselection of one or both, or add the requirement for an additionalinsulating layer (not shown). In a similar manner, it may be beneficialto create other electric or electrostatic charges on the depositionchamber 30 or on any other mechanical elements within the depositionchamber 30. As shown in FIG. 6, an internal baffle 122 may be used toprovide a more even distribution of color filter material 40 within thedeposition chamber 200. A charge may be applied to the internal bafflingby a baffle charging device 123.

[0059] Referring again to FIG. 2, deposition chamber 30 also provideseasy access for the insertion and removal of the substrate 14 throughaccess port 101. This process will potentially be automated bymechanical devices which are not shown. Access port 101 of depositionchamber 30 also provides access for the insertion and removal of themask 22 as well as for the proper placement of the mask 22. Maskalignment relative to the substrate 14 is key to this application andmay be manual or preferably, automated. Though it is shown oriented withthe substrate 14 facing upwards, this is not a requirement of theinvention. When attracting particles electrostatically, it may beadvantageous to orient the substrate 14 facing downward. In this manner,no debris from the deposition chamber 30 could inadvertently fall ontothe substrate 14.

[0060] The controlled environment can be used for post depositionprocessing of the deposited material on the substrate. Post depositionprocessing may involve the control of humidity, temperature, atmosphericconditions including pressure, and chemical composition of theatmosphere. As an example, many processes require the curing of thematerials to obtain desired functionality at elevated temperature. Thethermal control that is already built into the enclosure can be utilizedfor this purpose. Alternatively, the post processing required can bedone outside the enclosure.

[0061] It should be appreciated that deposition chamber 30 should alsobe designed so that there are no dead volumes that may result in theaccumulation of precipitated color filter materials 44 and so that itmay be easily cleaned. As such, it may be further partitioned into morethan one sub-chamber to facilitate the above (not shown). It may also beequipped with suitable mechanical devices to aid the precipitation anddeposition of color filter material 40. An example of such a devicewould be a mechanical agitator.

Embodiment II

[0062] Turning now to FIG. 5, another embodiment of deposition chamber100, contemplated by the invention, is shown. It contains many of thesame features previously described in the discussion of FIG. 2, with theaddition of a medium 111 which divides the deposition chamber 100 into apreparation sub-chamber 100 a and a deposition sub-chamber 100 b. Thematerials in these sub-chambers 100 a, 100 b are allowed to flow throughcontrollable dual chamber interface valve 110. Each sub-chamber 100 a,100 b is configured with independent control of pressure and temperaturethrough the use of pressure sensors 103, temperature sensors 104,pressure modulators 105, and temperature modulators 106. The preparationsub-chamber 100 a differs from the formulation reservoir 18 (FIG. 1) inthat the color filter material 40 can be (but is not necessarily)precipitated. The addition of a preparation sub-chamber 100 a to thesystem allows for a potentially large volume of prepared depositionmaterial to be ready and maintained at a higher than ambient pressurewhile still allowing the changing of substrate 14 and depositionmaterial through the access port 101.

Embodiment III

[0063] In FIG. 6, a simplified deposition chamber 200 is illustrated. Inthis embodiment, no provision is made for maintaining a pressure abovethat of ambient. Many of the other features described in FIGS. 2 and 5are still possible, but by no longer requiring the deposition chamber200 to support an elevated pressure, certain additional advantages canbe realized. For example, the substrate 14 no longer is required to becontained in deposition chamber 200. This is illustrated in FIG. 6 byshowing a moving substrate in the form of a web 120 that is transportedby conveyors 121. In such a system, it is possible to perform continuouscoating operations. In this case, a separate mask would likely not beused except for the case of a step and repeat process. Rather, a maskintegral to the substrate, as previously described, is the preferredmethod of achieving patterned deposition. Alternatively, a similarapproach, illustrated in FIGS. 2 and 5, could be used also without needfor access port 101.

[0064] Additional aspects of the invention may include multipledeposition chambers 30, 100, or 200, as illustrated in FIGS. 2, 5, and6, for coating multiple layers onto substrate 14. Alternatively,multiple masks 22 may be used such that a mask with a specificconfigurational structure of aperture patterns is used and subsequentlyreplaced with another shadow mask of different configurational structureof aperture patterns on the same substrate 14. Multiple masks, indexingof a mask, multiple layers, and multiple material processes are commonlyused in the manufacture of displays, therefore details and methods toprovide proper registration such as through the use of optical fiducialsare well known. The sequential process used for deposition of coloredmaterial(s) for display products applications may be interspersed withother processes, including deposition of other material(s) and/or posttreatment of deposited material(s), as needed, to create a desiredproduct.

[0065] General Architecture of a Color Filter

[0066] The general architecture of a color filter made in accordancewith the present invention will now be described. The color filter canbe a continuous film type or a pixellated array type. Additionally,either type of color filter can include one or a plurality of colorfilter materials.

[0067] Substrate

[0068] The substrate used with the invention can be any solid material,including an organic, an inorganic, a metallo-organic, a metallic, analloy, a ceramic, a synthetic and/or natural polymeric, a gel, a glass,or a composite material. The substrate can also have more than onelayer. For example, when the color filter is of the pixellated arraytype, the substrate can include a pre-patterned photoresist layercontaining selected openings over the pixel array. After depositing thecolor filter material, the pre-patterned photoresist layer can beremoved leaving the color filter material(s) in the opening position(s)over the pixel array. The photoresist layer can be created in any knownmanner.

[0069] Materials

[0070] The color filter material(s) can be any material delivered to asubstrate, to create a pattern on the substrate using deposition,etching, or other processes involving placement of a color filtermaterial on a substrate. The color filter material(s) can be selectedfrom species that are ionic and/or molecular of the types such asorganic, inorganic, metallo-organic, polymeric, oligomeric, metallic,alloy, ceramic, a synthetic and/or natural polymer, and a compositematerial.

[0071] For example, color filter materials which are useful in theinvention include, but are not limited to, the following:phthalocyanines, such as Pigment Blue 15, nickel phthalocyanine,chloroaluminum phthalocyanine, hydroxy aluminum phthalocyanine, vanadylphthalocyanine, titanyl phthalocyanine, and titanyltetrafluorophthalocyanine; isoindolinones, such as Pigment Yellow 110and Pigment Yellow 173; isoindolines, such as Pigment Yellow 139 andPigment Yellow 185; benzimidazolones, such as Pigment Yellow 151,Pigment Yellow 154, Pigment Yellow 175, Pigment Yellow 194, PigmentOrange 36, Pigment Orange 62, Pigment Red 175, and Pigment Red 208;quinophthalones, such as Pigment Yellow 138; quinacridones, such asPigment Red 122, Pigment Red 202, and Pigment Violet 19; perylenes, suchas Pigment Red 123, Pigment Red 149, Pigment 179, Pigment Red 224, andPigment Violet 29; dioxazines, such as Pigment Violet 23; thioindigos,such as Pigment Red 88, and Pigment Violet 38; epindolidiones, such as2,8-difluoroepindolidione; anthanthrones, such as Pigment Red 168;isoviolanthrones, such as isoviolanthrone; indanthrones, such as PigmentBlue 60; imidazobenzimidazolones, such as Pigment Yellow 192;pyrazoloquinazolones, such as Pigment Orange 67; iketopyrrolopyrroles,such as Pigment Red 254, Irgazin DPP RubinTR, Cromophtal DPP OrangeTR;Chromophtal DPP Flame Red FP (all of Ciba-Geigy); and bisaminoanthrones,such as Pigment Red 177.

[0072] The color filter material(s) can be a solid or a liquid.Additionally, the color filter material(s) can be an organic molecule, apolymer molecule, a metallo-organic molecule, an inorganic molecule, anorganic nanoparticle, a polymer nanoparticle, a metallo-organicnanoparticle, an inorganic nanoparticle, an organic microparticles, apolymer micro-particle, a metallo-organic microparticle, an inorganicmicroparticle, and/or composites of these materials, etc. Depending onthe specific application, it can be desirable to have apolymer-inorganic nanoparticle composite forming the color filtermaterial layer.

[0073] The color filter material(s) can be functionalized to dissolve,disperse and/or solubilize the color filter material(s) in thecompressed fluid. The functionalization may be performed by attachingfluorocarbons, siloxane, or hydrocarbon functional groups to the colorfilter material.

[0074] After suitable mixing with the compressed fluid, the color filtermaterial is uniformly distributed within a thermodynamicallystable/metastable mixture (either a dispersion or a solution) with thecompressed fluid (commonly referred to as the formulation). Theformulation may also contain a dispersant and or a surfactant to helpsolubilize and/or disperse the color filter material. The dispersantand/or surfactant can be selected from any group that will haveappropriate solubility in the compressed fluid medium as well as haveinteractions with the color filter material so that the color filtermaterial can be solubilized. Such materials include, but are not limitedto, fluorinated polymers such as perfluoropolyether, siloxane compounds,etc.

[0075] The formulation is maintained at a temperature and a pressuresuitable for the color filter material and the compressed fluid used ina particular application. A preferred range of formulation conditionsincludes a temperature in the range of 0 to 100° C. and/or a pressure inthe range from 1×10⁻² to 400 atm.

[0076] It is to be understood that elements not specifically shown ordescribed may take various forms well known to those skilled in the art.Additionally, materials identified as suitable for various facets of theinvention, for example, color filter materials, are to be treated asexemplary, and are not intended to limit the scope of the invention inany manner.

Parts List

[0077]10 system

[0078]12 delivery system

[0079]13 fluid delivery path

[0080]14 substrate

[0081]16 source of compressed fluid

[0082]18 formulation reservoir

[0083]20 discharge assembly

[0084]22 mask

[0085]24 closed loop control of the input valve

[0086]28 orifices/nozzles

[0087]30 deposition chamber or controlled environment

[0088]31 enclosure

[0089]32 shutter

[0090]33 viewing window

[0091]35 optical emitter

[0092]37 optical detector

[0093]39 microprocessor

[0094]40 color filter material

[0095]41 compressed fluids

[0096]42 formulation of color filter material 40

[0097]43 stream of color filter material 40

[0098]44 precipitated and/or aggregated color filter material

[0099]46 color filter material particles

[0100]47 nozzle opening

[0101]100 alternative embodiment of deposition chamber or controlledenvironment

[0102]100 a preparation sub-chamber

[0103]100 b deposition sub-chamber

[0104]101 access port

[0105]103 pressure sensor

[0106]102 a charging device

Parts List—Continued

[0107]102 b charging device

[0108]104 temperature sensor

[0109]105 pressure modulator

[0110]106 Temperature Modulator

[0111]107 particle charging device

[0112]108 flow control valve

[0113]109 source of compressed fluids

[0114]110 interface valve

[0115]111 medium

[0116]120 web

[0117]121 conveyor

[0118]122 internal baffle

[0119]123 baffle charging device

[0120]200 alternative embodiment of deposition chamber or controlledenvironment

What is claimed is:
 1. A method of forming a color filter comprising:providing a mixture of a color filter material and a compressed fluid;providing at least a partially controlled environment for retaining asubstrate, the at least partially controlled environment being in fluidcommunication with the mixture of the color filter material and thecompressed fluid; providing a shadow mask in close proximity to thesubstrate retained in the at least partially controlled environment; andchargably releasing the mixture of the color filter material and thecompressed fluid into the at least partially controlled environment,wherein the color filter material becomes free of the compressed fluidprior to contacting the substrate at locations defined by the shadowmask thereby forming a patterned deposition on the substrate.
 2. Themethod according to claim 1, wherein the color filter material is afirst color filter material and the shadow mask is a first shadow mask,the method further comprising: providing a mixture of a second colorfilter material and a compressed fluid; providing a second shadow maskin close proximity to the substrate retained in the at least partiallycontrolled environment; and chargably releasing the mixture of thesecond color filter material and the compressed fluid into the at leastpartially controlled environment, wherein the second color filtermaterial becomes free of the compressed fluid prior to contacting thesubstrate at locations defined by the second shadow mask.
 3. The methodaccording to claim 1, wherein the color filter material is a first colorfilter material, the method further comprising: providing a mixture of asecond color filter material and a compressed fluid; indexing the shadowmask; and chargably releasing the mixture of the second color filtermaterial and the compressed fluid into the at least partially controlledenvironment, wherein the second color filter material becomes free ofthe compressed fluid prior to contacting the substrate at locationsdefined by the indexed shadow mask.
 4. The method according to claim 1,wherein the substrate is flexible.
 5. The method according to claim 1,wherein the substrate is rigid.
 6. The method according to claim 1,wherein the color filter material is selected from the group consistingof phthalocyanines, isoindolinones, isoindolines, benzimidazolones,quinophthalones, quinacridones, dioxazines, thioindigos, epindolidiones,anthanthrones, isoviolanthrones, indanthrones, imidazobenzimidazolones,pyrazoloquinazolone, siketopyrrolopyrroles, and bisaminoanthrones.